Fix inline comment links for non-visible comments

Summary: Ref T2222. Restore this funky is-visible / inline-is-elsewhere logic.

Test Plan: Updated a revision, saw all the inlines render properly when looking at various diffs and versus-diffs. Clicked inline links.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2222

Differential Revision: https://secure.phabricator.com/D8224